1. Field of the Invention
The present invention relates generally to an illumination device, and more particularly to an illumination device which utilizes an appropriate optical lens, a light emitting unit and a light reflector in such a manner to collect all of the light beams within a predetermined range, thereby providing the maximum illumination effect.
2. The Prior Arts
One problem encountered presently when designing the application of a light emitting diode (LED) device is how to arrange the components in order to achieve extra illumination from the secondary light beam. The optical lens implemented in a conventional illumination device generally provides an illumination range, which is insufficient in brightness so as to cause blur vision on the illuminated spot. Insufficiency of brightness may result in discomfort to a viewing person and finally leads to visual fatigue. The manufacturers of LED devices have noted the presently existing problem and are searching urgently a way to develop an LED device that is capable of providing comfortable visual effect to a viewer in addition to providing the maximum illumination effect.
FIG. 1 illustrates a conventional LED device, which includes a light reflector 1a, an LED module 2a disposed at the bottom of the reflector 1a, and a slab lens 3a disposed above the reflector 1a. It is noted that the slab lens 3a protects the LED module 2a from being damaged and does not provide a secondary light beam, all of the light beams is emitted from the LED module 2a in a single way and the light beams are not reflected from the reflector 1a. 
As best shown in FIG. 1, when the emitting light angle from the LED module 2a is at 140°, only the light beams from 20°˜48.59° and 131.4°˜160° are reflected from the reflector 1a. Note that only the above-mentioned light beams within the above-stated degrees are controllable. The remaining light beams are out of bound of the reflection range and hence the reflector 1a fails to collect all the light beams into a predetermined range, thereby providing insufficient illumination effect.
FIG. 2 illustrates another conventional LED device, which includes a secondary optical lens unit 4a disposed above an LED module 2a. The middle of the secondary optical lens unit 4a is in the form of a convex lens 41a, which has two outwardly curved sides serve as reflection structure for emitting a small emitting angle owing to the refraction performance of the convex lens 41a. In other words, the convex lens 41a is capable of converting the initial small emitting angle of the LED module 2a c into a smaller emitting angle owing to the refraction (or the secondary optical effect), thereby collecting the light beams at the middle portion. Note that the light beams at two sides of the LED module 2a are not enhanced by the refraction performance or the secondary optical effect but rather scatter away from the middle, thus the target spot may suffer non-uniform illumination density.
The non-uniform illumination density may result in discomfort to a viewing person and finally leads to visual fatigue. Therefore, a critical problem to be solved urgently is how to improve the collection of all the scattered emitted light beams into a predetermined range so as to provide the maximum illumination with uniform density.